Faculty members are well aware of the importance of letters of recommendation. Students seeking such letters should ask the two or three faculty members who know their work best—generally faculty members will not write letters for students unless they have had them in several classes. Requests should be made several weeks prior to any deadlines for letters. While most faculty members will try to cooperate to the fullest extent possible, students should not just assume that they will agree to write a letter.
Faculty members may not feel that they know the student's work well enough or they may not feel that they can honestly offer a sufficiently positive recommendation. If a faculty member declines, remember that it is better to have no letter of recommendation than to have a weak letter of recommendation. Where a faculty member does agree to write a letter of recommendation, the student should recognize that it takes time to respond to such requests and should provide in writing to the faculty member the information necessary to ensure a good letter (courses taken, student's background, student's other academic activities and interests, etc.).
Faculty members may also request copies of papers and exams that the student wrote for their courses, so keep them in a safe place! It is a good idea to provide the faculty member with phone numbers so that they can contact you if they have any questions as they write the letters. Students should remember to fill out the forms completely before they are given to the faculty member.
While students may ask for either "open" or "confidential" letters of recommendation, they should recognize that the "open" ones are generally dis-valued, and they should respect the confidentiality of the recommendation if they ask for such a letter.